Direct preparation of 3D monolithic carbon-structured Ti₃C₂-MXene electrodes for capacitive deionization with laser-driven carbonization method

Two-dimensional inorganic compounds (MXenes) are considered as advanced materials for capacitive deionization (CDI) in water treatment, however, nanosheet MXenes are highly susceptible to self-stacking and their oxidative stability in aqueous environments is low. In this study, the film-forming properties of polyimide (PI) were employed for facile construction of carbon nanotube (CNT)-bridged MXene films (CNT/PI@MXene) on carbon cloth without the use of binders. CNT/PI@MXene was rapidly laser carbonized to form a threedimensional (3D) monolithic structure (CNT-PIC@MXene), with the carbonized PI (PIC) acting as an intrinsic pillar and protective shell for Ti3C2-MXene to prevent stacking and oxidation, while CNT formed interconnections of Ti3C2-MXene layers to enhance electrical conductivity. The as-prepared CNT-PIC@MXene electrodes possessed a capacitance of 222.3 F center dot g(-1) and exhibited good cyclic stability (100 % capacitance stability after 1000 cyclic voltammetry cycles), and had superior salt adsorption capacity (46.8 mg center dot g(-1), 2.8 mg center dot g(-1)center dot min(-1)) with 89.7 % desalination retention after 30 CDI cycles. The method developed in this work addresses issues of self-stacking and water-assisted oxidation of Ti3C2-MXenes and demonstrates binder-free preparation of MXene-based electrodes for CDI desalination applications.